LSM/SELinux: inode_{get,set,notify}secctx hooks to access LSM security context information.

This patch introduces three new hooks. The inode_getsecctx hook is used to get
all relevant information from an LSM about an inode. The inode_setsecctx is
used to set both the in-core and on-disk state for the inode based on a context
derived from inode_getsecctx.The final hook inode_notifysecctx will notify the
LSM of a change for the in-core state of the inode in question. These hooks are
for use in the labeled NFS code and addresses concerns of how to set security
on an inode in a multi-xattr LSM. For historical reasons Stephen Smalley's
explanation of the reason for these hooks is pasted below.

Quote Stephen Smalley

inode_setsecctx:  Change the security context of an inode.  Updates the
in core security context managed by the security module and invokes the
fs code as needed (via __vfs_setxattr_noperm) to update any backing
xattrs that represent the context.  Example usage:  NFS server invokes
this hook to change the security context in its incore inode and on the
backing file system to a value provided by the client on a SETATTR
operation.

inode_notifysecctx:  Notify the security module of what the security
context of an inode should be.  Initializes the incore security context
managed by the security module for this inode.  Example usage:  NFS
client invokes this hook to initialize the security context in its
incore inode to the value provided by the server for the file when the
server returned the file's attributes to the client.

Signed-off-by: David P. Quigley <dpquigl@tycho.nsa.gov>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>

1 files changed, 29 insertions, 0 deletions

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 134a9c0..7118be2 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -5351,6 +5351,32 @@ static void selinux_release_secctx(char *secdata, u32 seclen)
 	kfree(secdata);
 }
 
+/*
+ *	called with inode->i_mutex locked
+ */
+static int selinux_inode_notifysecctx(struct inode *inode, void *ctx, u32 ctxlen)
+{
+	return selinux_inode_setsecurity(inode, XATTR_SELINUX_SUFFIX, ctx, ctxlen, 0);
+}
+
+/*
+ *	called with inode->i_mutex locked
+ */
+static int selinux_inode_setsecctx(struct dentry *dentry, void *ctx, u32 ctxlen)
+{
+	return __vfs_setxattr_noperm(dentry, XATTR_NAME_SELINUX, ctx, ctxlen, 0);
+}
+
+static int selinux_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen)
+{
+	int len = 0;
+	len = selinux_inode_getsecurity(inode, XATTR_SELINUX_SUFFIX,
+						ctx, true);
+	if (len < 0)
+		return len;
+	*ctxlen = len;
+	return 0;
+}
 #ifdef CONFIG_KEYS
 
 static int selinux_key_alloc(struct key *k, const struct cred *cred,
@@ -5550,6 +5576,9 @@ static struct security_operations selinux_ops = {
 	.secid_to_secctx =		selinux_secid_to_secctx,
 	.secctx_to_secid =		selinux_secctx_to_secid,
 	.release_secctx =		selinux_release_secctx,
+	.inode_notifysecctx =		selinux_inode_notifysecctx,
+	.inode_setsecctx =		selinux_inode_setsecctx,
+	.inode_getsecctx =		selinux_inode_getsecctx,
 
 	.unix_stream_connect =		selinux_socket_unix_stream_connect,
 	.unix_may_send =		selinux_socket_unix_may_send,